The present invention relates to security seals and more particularly to security seals of the padlock type that include color coded indicators for providing visual evidence of tampering.
Security seals of the padlock type are generally well known, and they hae found wide spread use as a means for sealing structures such as currency bags, closures, electric meters, and the like. Examples of such seals may be found in the following U.S. Pat. Nos.: 3,375,033; 3,485,521; 4,278,281; 4,353,583 and 4,687,240. All of these seals generally have a plastic body with a pair of spaced cavities and a U-shaped shackle having ends that are permanently locked in the cavities when the seals are used. A number of these prior art seals have been designed to produce a visual indication of tampering. For example, in U.S. Pat. No. 4,687,240, the seal body is made of a pigmented plastic of a type which produces a white blush when deformed. If tampering occurs, the shackle deforms the plastic body to produce a milky white appearance that is readily visible. Additionally, because the shackle has sharp ends to deform the plastic, the shackle ends will, in some cases, protrude from the seal body giving an added visual indication of tampering. Other examples of visual indicators may be found in the above cited prior art U.S. Pat. Nos. 4,278,281 and 4,353,583.
Although such devices have served the purpose, they have not proved entirely satisfactory under all conditions of service for the reason that a number of these seals have been defeated by people who manufacture a copy or otherwise produce a duplicate seal to be used as a replacement during tampering. Those concerned with such seals have long recognized the need of providing a security seal having a tampering indicator means that is highly visable after tampering but is highly concealed before tampering and, therefore, difficult to duplicate.
One attempt to improve the visual characteristics of security seals and discourage duplication includes the use of a colored dye that will seep from the seal onto the surrounding structures when tampering occurs. Examples of prior art devices of this nature may be found in the following U.S. Pat. Nos.: 3,991,594; 3,463,532; and 4,326,741. These patents generally describe security seals having a chamber in which a dye is stored. When the seal is broken, the chamber is penetrated with a cutting tool and the dye is ejected. As such, the dye will stain the outer surface of the tubing and/or stain the surrounding structures and even the hands of the person tampering with the tube.
The advantages of such dye filled security seals are numerous. One such advantage being that it becomes easier to determine, even from substantial distances, that the seal has been compromised. Also, such dyes can provide on-site evidence that tampering has occurred plus evidence of the person or tools used to effect the tampering. Although seals of the prior art and of my co-pending application are very useful and adequate for most purposes, there are applications where a higher degree of security is required. Thus, an enterprising thief with adequate resources can duplicate seals with dye indicators by constituting the appropriate molds and obtaining dyes or dye filled ampules with dyes of the same color as those being used. In such a case the seal can be removed by cutting the shackle and, after the protected container is violated, a new seal which is apparently identical substituted for the old seal. Needless to say that where high security is a requirement, such a possibility for successful defeat of the seal is unacceptable.
It is, therefore, an object of the present invention to provide a security seal that discourages tampering by seal duplication.
Another object of the invention is to provide a security seal that provides a distinct, highly visible indication of tampering.
Yet an additional object of the invention is to provide a security seal with dye wherein the telltale color of the dye does not become evident until after tampering.